Local manipulation of image layers using standard image processing primitives

In any modern, standard image manipulation program, images are made up of multiple layers ordered on top of each other in a user defined sequence. A layer is a collection of graphical objects (like masks and image patches). Each layer can be edited separately and then all the layers are composited together to get the final image. In some images, however, we need to change the order of stacking at multiple areas of overlap for the same set of layers without creation and manipulation of individual layers at each position of overlap. This problem is solved by the concept of Local Layering as given by McCann and Pollard [10]. Their technique was, however, presented as a standalone idea, making its use difficult in standard image processing pipelines. In this paper, we present a novel implementation of local layering using a combination of standard image processing primitives. We show that it is possible to locally align layers while simultaneously continuing to also use the global alignment of layers via an efficient use of image masks. All our ideas are implemented as a plug-in addition to the GIMP, however, the algorithms we present are general and implementable in any standard image processing pipeline.